Insulating foundation for a low temperature storage tank

ABSTRACT

1,182,578. Liquefied gas storage containers. PITTSBURGH-DES MOINES STEEL CO. 12 July, 1968 [2 Feb., 1968], No. 33297/68. Heading F4P. A cylindrical flat-bottomed inner cold liquefied gas storage tank is supported by a plurality of spaced modules 40, 70&#39;Fig. 4 located between the tank bottom 30 Fig` 1 and the flat bottom 20 of an outer tank and rigidly connected together by planking 90, and the spaces between the modules and that between the cylindrical side walls 32, 22 of the inner and outer tanks are filled with heat insulating material e.g. expanded perlite or mineral wool. The modules 40 which are peripherally arranged beneath the inner tank wall 32 comprise radially extending wood blocks 42, 46, tangential blocks 44 therebetween and top plates 50 all nailed together, whereas modules 70 which support the tank bottom 30 comprise hollow rectangular frames filled with loose insulation 62 and to which are nailed the planks 90. The latter are also nailed to shoulders 56 on modules 40. The exterior of wall 32 is secured by anchor straps 66 which pass between the sector-like space between blocks 40, through a concrete levelling pad (58) Fig. 3, (not shown) and into a concrete foundation 16 supported by piles 14.

June 2, 1970 A. H. NELSO N 3,514,913

INSULATING FOUNDATION FOR A Low TEMPERATURE STORAGE TANK Filed Feb. 2.1968 2 Sheets-Sheet 1 ARD ELL H. NELSON BY WM We ATTORNEYS A. H. NELSONJune 2, 1970 INSULATING FOUNDATION FOR A LOW TEMPERATURE STORAGE TANKFiled Feb. 2. 1968 2 Sheets-Sheet 2 INVENTOR ARDELL H. NELSON ATTORNEY-SUnited States Patented June 2, 1970 US. Cl. 52249 2 Claims ABSTRACT OFTHE DISCLOSURE An inner tank is supported in spaced relationship to anouter tank, the inner tank being supported by a plurality of spacedhollow modules each of which is formed of a plurality of interconnectedwooden members. The space between and within the hollow modules as wellas the space between the walls of the inner and outer tanks are filledwith an insulating material. The various modules supporting the innertank are interconnected by wooden planking so as to unitize and rigidizethe support means for the inner tank.

BACKGROUND OF THE INVENTION This invention relates to the constructionof a tank for storing low temperature liquids.- Low temperature storageis defined as storage at a temperature of +32 F. or lower. Thisinvention is more particularly concerned with an insulating foundationsystem for storage tanks in low temperature service.

When storing substances at atmospheric pressures, it is necessary thatlow temperatures be used in order for normally gaseous substances toremain in the liquid state. These low temperature liquids are normallystored in heavily insulated tanks. Quite often, these tanks are the flatbottom cylindrical type for economic reasons. When such a flat bottomtype of tank is used, it is necessary to provide an insulatingfoundation under the bottom of the tank. This foundation must have goodinsulating qualities and also have sufiicient strength to support theweight of the storage tank and its contents. It must also enable easyand economical construction thereof.

Conventional foundation materials for low temperature storage tanks inthe past have consisted of air entrained solids such as foamglass, andother materials, such as insulating concerete. Convention-a1 foundationmaterials and systems presently being used present a number ofdisadvantages. For example, foamglass may be used for moderate loads,but, it has a high unit cost. If used under conditions of heavy loading,it has a tendency to crush find deflect excessively which in turncreates design probems.

Light aggregate insulating concrete, on the other hand, while being ofsomewhat lower cost, presents other problems. Excessive heat ofhydration can possibly be created by monolithicly placing a large massof such insulating concrete. In addition, a large mass of such concretemay not have dried sufiiciently within a reasonable time afterplacement. Care must be taken to avoid excessive Water in mixinginsulating concrete since the light Weight particles may be floated thuscreating voids which could break down under load from the tank contents.

It is extremely difiicult to dry light aggregate insulating concreteeven in very thin sections. Units having a thickness of 4 or 5 inchesusually contain between and percent of retained moisture even afterextended periods of drying. With this amount of retained moisture, the Kvalue of insulating concrete normally used would be of the order of 1.6to 1.8 B.t.u. per hour-sq. foot-inch of thickness-degree temperaturediflerential. With this high value of thermal conductivity, thethickness of the bottom insulation system must be increased in order toreduce the amount of heat going into the tank. With this increase inthickness, the cost of the insulating system is therefore increasedaccordingly. Lightweight aggregate insulating units that are sometimesused for insulating foundations must be mnaufactured at special plantsto control the quality of the finished product.

SUMMARY OF THE INVENTION In the present invention, the inner tank whichis disposed in spaced relation to the outer tank is supported by aplurality of spaced hollow modules having loose fill insulation disposedtherebetween and also therewithin. The loose fill insulation which maybe expanded perlite or mineral wool and the like, is inexpensive, andthe modules are formed of a pluarlity of interconnected wooden mem-'bers or timbers. Means in the formof planking which comprises aplurality of wooden members is employed for interconnecting the moduleswith one another to unitize and rigidize the support means for the innertank. This arrangement is unique and has not been employed in the priorart.

The bottom insulating system described herein has many advantages overprior state of the art. The timber used for both the shell supportmodules and the bottom support modules has a greater compressivestrength than light aggregate concrete, therefore the amount ofmaterials may be reduced accordingly. The ultimate strength of thetimber is higher at low temperatures than at atmospheric temperatures.Since this oven dry state (for insulating concrete) is impractical toattain or maintain, the timber used as structural support has a distinctadvantage in that it reduces the amount of heat conducted into the tank.The timber used for the shell support modules and the bottom modules isalso less expensive than an qeuivalent amount of light aggregateinsulating concrete to carry the same load. Since the height of thebottom supoprt modules may be accurately controlled 'by sawing ofi thetimber to the proper length, the use of unfinished lumber is possible.

Both the shell support modules and the bottom support modules may beconstructed with ease by the use of unskilled personal. This featurepermits these components to be assembled anywhere. Since the componentsin the particular system described herein may be assembled at anyconstruction site, the shipping problems are reduced accordingly. Sincethe amount of structural support can be reduced by using the timber(when compared to the amount of lightweight aggregate insulating units),the amount of loose fill insulation may he proportionately increased.This further achieves better over-all economy since the thermalconductivity of this loose fill material is better than either timber orlightweight aggregate insulating concrete, and the price of this loosefill insulation material is considerably less than either timer or thelightweight aggregate insulating concrete.

The foundation of the present invention may be employed with tanks ofany diameter with relative ease by simply varying the amount and spacingof the various components. The timber making up the shell supportmodules and the bottom support modules and the bottom planking may betreated to make it both fire retardant and decay resistant. Since thetimber units are much stronger than lightweight aggregate insulatingconcrete units, they may be easily handled without the chipping andbreakage problems associated with lightweight insulating concrete. Thisprecludes the possibility of having lightweight insulating concreteunits installed as a support system containing hidden cracks which could'break down under the load imposed by the tank contents.

3 BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an elevation partly brokenaway and in section illustrating a low temperature storage tankincorporating the insulating foundation of the present invention;

FIG. 2 is a view on an enlarged scale taken substantially along line 2-2of FIG. 1 looking in the direction of the arrows, and being broken awayfor the sake of clarity;

FIG. 3 is an enlarged sectional view of a portion of the structureillustrated in FIG. 1;

FIG. 4 is a top perspective view partly broken away illustrating thearrangement of the modules and planking for supporting the inner tank;

FIG. 5 is a sectional view taken substantially along line 55 of FIG. 3looking in the direction of the arrows; and

FIG. 6 is a sectional view taken substantially along line 66 of FIG. 4looking in the direction of the arrows.

DESCRIPTION OF THE PREFERRED EMBODIMENT I Referring now to the drawingswherein like reference characters designate corresponding partsthroughout the several views, a low temperature storage tank isindicated generally by reference numeral 10 in FIG. 1, the tank beingsupported above the ground level indicated by reference numeral 12 by aplurality of piles 14 extending upwardly from the ground. These pilesmay be supported by friction from contact with the earth and/ or by endbearing on suitable soil strata (not shown) disposed at a suitabledistance below the ground level. A support means in the form of asupporting pile cap foundation 16 is provided formed of concrete orsimilar material having the necessary strength for supporting the weightof the tank.

The storage tank includes an outer tank and an inner tank, the outertank comprising a bottom wall 20 which is substantially flat, asubstantially cylindrical side wall 22 extending upwardly from thebottom wall, and a top wall 24 closing off the upper end of the outertank, this top wall being generally dome-shaped in configuration as seenin FIG. 1. The walls of the tank are formed of a suitable structuralmaterial such as steel or the like adapted to withstand the pressuresapplied thereto during .use in the tank, the walls being suitablysecured to one another as by welding or the like.

The inner tank of the storage tank includes a bottom Wall disposedsubstantially parallel with the bottom wall 20 of the outer tank, theinner tank also including a substantially cylindrical side wall 32disposed inwardly of the side wall 22 to define an annular spacetherebetween. The inner tank also includes a top wall (not shown) whichis also generally. of dome-shaped configuration and spaced from the topwall 24 of the outer tank. The space between the side walls of the twotanks as well as the space between the top walls thereof is filled witha loose fill insulation indicated generally by reference numeral 36 asis conventionally employed in low temperature storage tanks. This loosefill insulation may comprise in a typical example a granular materialsuch as expanded perlite or a fibrous insulating material such asmineral wool and the like. Any suitable loose fill insulation may beemployed for this purpose.

The inner tank is supported in the position illustrated by a pluralityof modules, and as seen most clearly in FIG. 2, a first plurality ofspaced shell support modules are indicated generally by referencenumeral 40, these shell support modules being disposed in an annularspaced array so as to be disposed substantially beneath the side wall 32of the inner tank.

Referring now particularly to FIGS. 3 and 4, the construction of theshell sup-port modules is clearly illustrated. Each of these shellsupport modules comprises a 4- plurality of interconnected timbers orwooden members. While a specific arrangement of timers is illustrated,it will be readily recognized that each of the shell support modules maybe built up as desired utilizing a plurality of timbers to afford thedesired size and strength.

As illustrated each of the shell support modules 40 includes a firstplurality of timbers or blocks 42 disposed in edge-to-edge relationshipwith one another and extending substantially radially of the storagetank. A second plurality of timbers or blocks 44 are supported on theupper surface of the timbers 42, timbers 44 also being disposed inedge-to-edge relationship with one another and extending substantiallytangentially with respect to the storage tank. Each of the shell supportmodules also includes a third layer of timbers or block 46 disposed inedge-to-edge relationship with one another and supported on timbers 44,the timbers 46 being disposed substant ally parallel with the timbers orblock 42. All of these various timbers 42, 44 and 46 are suitablyfastened together by means of fasteners 48 extending through thetimbers. These fasteners are illustrated comprising elongated nalls,although it should be understood that any suitable fastener means suchas bolts or the like may be employed for rigidly securing the timberstogether to provide an integrated module.

Each of the modules also includes a wooden timber or flat member 50secured to the upper surface thereof by a plurality of fasteners such asnails 52, it being noted that the edge 54 of member 50 as seen in FIG. 4terminates short of the inner edge of the remainder of the module todefine a radially inwardly positioned shoulder 56, these inner shoulderson the various modules serving to support the planking hereinafterdescribed.

As seen especially in FIG. 3, a thin concrete levellng base 58 is castover the bottom Wall 20 of the outer tank and comprises a leveling padso as to provide a level foundation for the various support modules.

The shell support modules as well as the bottom support moduleshereinafter described are supported on the upper surface of thisleveling pad so that the inner tank will be properly supported inposition. The leveling pad may be formed of regular concreteapproximately 6 inches in thickness.

As seen particularly in FIG. 5, adjacent shell support modules 40 aredisposed with respect to one another such that the facing ends 4%thereof are spaced apart to define a wedge-shaped space therebetween. Abody of Fiberglas or similar material 60 is stiffed or forced into thisspace so as to be positioned in the location illustrated in FIG. 5 so asto retain loose fill insulation 62 inwardly thereof, this loose fillinsulation as described hereinafter completely filling the space betweenthe various bottom support modules of the foundation. This insulation isalso disposed within the hollow modules.

The bodies of Fiberglas 60 extend vertically between the leveling pad 20upon which the shell support modules are supported to the undersurfaceof the bottom wall 30 of the inner tank which rests upon the uppersurface of members 50 of the shell support modules.

A plurality of shell anchor straps (or anchor bolts) 66 are provided,the upper ends of these straps being suitably secured as by welding tothe outer surface of the side wall 32 of the inner tank, the shellstraps extending down between adjacent spacing shell support modules asseen in FIG. 5, the anchor straps continuing downwardly and having thelower offset ends 68 thereof embedded within the material of the pilecap foundation 16 as seen most clearly for example in FIGS. 1 and 3. Itis apparent that the relationship of the anchor straps and the bodies ofFiberglas material as seen in FIG. 5 are such that the anchor strapswill tend ot hold the Fiberglas bodies 60 in operative position whensubjected to pressure from the inner side thereof by the loose fillinsulation bearing thereagainst. The use of anchor bolts in lieu ofanchor straps will provide adjustment to compensate for differentialcontraction of the shell and anchor during cooldown.

As seen most clearly in FIG. 2, a plurality of bottom support modulesindicated generally by reference numeral 70 are provided. A large numberof these modules are provided in substantially equally spacedrelationship beneath the bottom wall of the inner tank. The size andspacing of these bottom support modules will of course vary inaccordance with the size of the tank and the load to be supported.Although only certain ones of the bottom support modules 70 areillustrated in FIG. 2, it should be understood that they will bedisposed throughout the area beneath the bottom wall of the inner tankin substantially equally spaced relationship.

Referring now to FIGS. 4 and 6, the construction of the bottom supportmodules may be clearly understood. Each of the bottom support modules 70is formed of four substantially identical rectangularly shaped timbersor planks 72, 74, 76 and 78 which are interconnected in the manner shownby suitable fasteners 80 comprising spikes, bolts, nails and the like toform hollow post-like sections. It is apparent that the bottom supportmodules each comprise a hollow construction adapted to receive loosefill therewithin.

Means for interconnecting the modules with one another comprisesplanking, this planking including a plurality of adjacent timbers 90disposed in edge-to-edge relationship as seen most clearly for examplein FIGS. 3 and 4, these timbers being suitably secured to the respectivemodules by means of suitable fasteners such as spikes, bolts, nails andthe like 92. The outer peripheral edge portion of the over-all plankingis supported on the radially inner shoulders 56 of the shell supportmodules previously described, while the joints between the variouslengths of planking aligned with one another are designed to be disposedover one of the bottom support modules. The individual members 90 of theplanking are supported on the upper ends of the bottom support modules.

The loose fill insulation 62 previously described is adapted tosubstantially fill the space between the bottom support modules 70 aswell as the space within the hollow interiors thereof, this loose fillinsulation extending between the bottom wall 20 of the outer tank andthe undersurface of the planking, and also extending between adjacentsheel support modules as previously described in connection with FIG. 5of the drawings.

It is apparent from the foregoing that there is provided a new and novelinsulating foundation for a low temperature storage tank wherein theinner tank is supported by a plurality of spaced hollow modules havingloose insulation disposed therebetween, and therewithin, these modulesbeing formed of wooden material to provide the aforementionedadvantages. The modules are interconnected with one another by theplanking so as to unitize and rigidize the support means for the innertank.

As this invention may be embodied in several forms without departingfrom the spirit or essential characteristics thereof, the presentembodiment is therefore illustrative and not restrictive, and since thescope of the invention is defined by the appended claims, all changesthat fall within the metes and bounds of the claims or that form theirfunctional as well as conjointly cooperative equivalents are thereforeintended to be embraced by those claims.

I claim:

1. An insulating foundation for a low temperature storage tankcomprising an outer tank including a side wall and a bottom wall, aninner tank including a side wall spaced inwardly of the side wall ofsaid outer tank, insulation provided between said side walls of theinner and outer tanks, said inner tank also including a bottom wallspaced inwardly of the bottom wall of said outer tank, said inner tankbeing supported by a plurality of spaced modules having insulationdisposed therebetween, and means interconnecting said modules with oneanother to unitize and rigidize the support means for the inner tank,said modules including first a plurality of circumferentially spacedshell support modules of face contacting blocks disposed substantiallybeneath the side wall of said inner tank, said modules also including asecond plurality of spaced bottom support modules of hollow postlikeplank-formed sections disposed inwardly of said first modules andsubstantially beneath the bottom wall of said inner tank.

2. An insulating foundation for a low temperature storage tankcomprising an outer tank including a side wall and a bottom wall, aninner tank including a side wall spaced inwardly of the side wall ofsaid outer tank, insulation provided between said side walls of theinner and outer tanks, said inner tank also including a bottom wallspaced inwardly of the bottom wall of said outer tank, said inner tankbeing supported by a plurality of spaced modules having insulationdisposed therebetween, and means interconnecting said modules with oneanother to unitize and rigidize the support means for the inner tank,said plurality of modules including a first plurality of spaced shellsupport modules face contacting wooden blocks disposed substantiallybeneath the side wall of said inner tank and a second plurality ofspaced bottom support modules of hollow post-like wooden sectionsdisposed beneath the bottom wall of said inner tank, each of said shellsupport modules comprising a plurality of interconnected wooden members,the insulation disposed between said modules comprising loose fillinsulation substantially filling the space 'between said modules, meansfor retaining said loose fill insulation in position, said shell supportmodules defining shoulders thereon, the means for interconnecting saidmodules with one another comprising a plurality of wooden membersdefining planking, the edges of said planking being supported on saidshoulders, said planking also being supported on the upper ends of saidbottom support modules, the planking being rigidly attached to saidshell support modules and said bottom support modules, the. bottom wallof said inner tank resting upon and being supported by said planking.

References Cited UNITED STATES PATENTS 2,520,883 8/1950 Kornemann et al.220-18 3,076,317 2/ 1963 La Fave 52249 3,338,010 8/1967 Waugh 52249FOREIGN PATENTS 188,513 9/1907 Germany.

FRANK L. ABBOTT, Primary Examiner I. L. RIDGILL, 1111., AssistantExaminer US. Cl. X.R.

